Problem: $ {3\cdot \left[ \begin{array}{cc} 4 & -2 \\ -1 & 4 \end{array} \right]=}$
Solution: The Strategy To multiply a matrix by a scalar, we multiply each term of the matrix by the scalar. Multiplying each term $ {\begin{aligned}3\cdot \left[\begin{array}{rr} {4} & {-2} \\ {-1} & {4} \end{array}\right]&=\left[\begin{array}{rr} 3\cdot{4} & 3\cdot{-2} \\ 3\cdot{-1} & 3\cdot{4} \end{array}\right] \\\\&=\left[\begin{array}{rr} {12} & {-6} \\ {-3} & {12} \end{array}\right]\end{aligned}}$ Summary $ {3\cdot \left[ \begin{array}{cc} 4 & -2 \\ -1 & 4 \end{array} \right]=\left[ \begin{array}{cc} 12 & -6 \\ -3 & 12 \end{array} \right]}$